The answer is obvious! Gordon Freeman. I think it would be hard to slit his throat even if he is caught in that, because and correct me if I'm wrong- he wears a protective thingy around his neck. that I think keeps the Barnicles from killing him. Because I think that the Barnacles can strangle people or crush bones before they actually reach the Barnicles mouth. Plus, Gordon is awesome, and in a way, he's actually thousands of people. And I think that he's strong enough to flip Sam over from that position.